150 PSYCHOLOGICAL EFFECTS OF ALCOHOL. 



muscle, or increased adequacy of coordinated inhibition of antago- 

 nistics any or all of these might operate to increase the velocity of 

 movement. A change in the relationship of the different factors which 

 involves the preponderance of any one of the opposing tendencies must 

 decrease or increase the time of movement, according to the direction 

 of the change and the nature of the tendency. 



It was in obedience to our fundamental principles for the selection of 

 measurable phenomena that we planned to measure the velocity of 

 movement of the lightest practicable moving member, in an act which 

 was as far as possible removed from arbitrary or voluntary interference. 

 In both respects the organ in which Sherrington first demonstrated the 

 phenomena of reciprocal innervation in voluntary movements is pecul- 

 iarly satisfactory. The eye is one of the lightest of moving members 

 and the leverage of its muscular attachments is the most favorable 

 for rendering its mass a negligible factor. Eye-movements of the first 

 type, that is. simple movements of the eye in fixating peripherally seen 

 objects, are relatively independent of voluntary control. Moreover, 

 these movements of the eye, in which the point of regard wanders over 

 any relatively fixed section of the field of vision, are doubtless the most 

 numerous, and at the same time the best understood, of all the eye- 

 movements. 



EFFECT OF ALCOHOL ON THE VELOCITY OF EYE-MOVEMENTS 



OF THE FIRST TYPE. 



The most important differentiating characteristics of this class of eye- 

 movements were noted by Dodge 1 in his description of the type from 

 photographic records, as follows: The duration of eye-movements of 

 the first tvpe is less than of any other movement of the eve. It varies 



V X v k. 



directly with the angle of displacement, but is approximately constant 

 for each individual under the same conditions of fatigue of the eye- 

 muscles, of original orientation, and of the direction and angle of eye- 

 movement. 



If we were dependent on subjective data alone, almost everyone 

 would say without hesitation that he could move his eye across the 

 field of vision rapidly or slowly at will. That is, however, an illusion. 

 The effort to move the eye slowly from one point of regard to another 

 always results in one or more complete stops, of which the subject is 

 never directly conscious until his attention is called to them. The 

 simplest method of convincing oneself of this fact is the method of 

 Brown.- If the attempt be made to move the eyes slowly along a line 

 which passes through a bright light, on closing the eyes a number of 

 well-defined after-images of the light will be observed, clearly indicating 

 that the eye rested at corresponding points along the path. More 



'Dodge, Am. Journ. Physiol.. 190:>, 8, p. 307. -Brown, Nature, 1S95, 52, p. 184. 



